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Why Lense-Thirring solid-body precession cannot produce the LFQPOs observed in X-ray binaries

Presentation #406.02 in the session “Stellar/Compact II (Oral)”.

Published onApr 01, 2022
Why Lense-Thirring solid-body precession cannot produce the LFQPOs observed in X-ray binaries

The timing properties of X-ray binaries are still not understood, particularly the presence of quasi-periodic oscillations (QPOs) in their X-ray power spectra. The solid-body regime of Lense-Thirring precession is one prominent model invoked to explain the most common type of QPOs, Type C. However, solid-body precession requires a specific structure that has not been examined in light of constrained properties of accretion flows. During this talk, I will explore the different observational constraints on the accretion flow and compare them to the structure required by the solid body precession. I will show that, in order to reproduce the observed X-ray spectra during luminous hard states, the hot flow must accrete at sonic to supersonic speeds, unreachable with typical viscous torques. As a result of this extreme accretion speed (or high α parameter), no region of the disk during these states lies in the “wave-like” regime required for solid-body precession. Furthermore, we expect the flow to align with the black hole spin axis via the Bardeen-Petterson effect inside a radius rbreak > rt. As a consequence, the hot inner flow cannot exhibit solid body precession — as currently pictured in the literature — during luminous hard states. Since Type C QPOs are prevalent in these states, we conclude that this mechanism is unlikely to be responsible for producing Type C QPOs around stellar mass black holes.


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